Effective Treatment of Helicobacter pylori Infection Using Supramolecular Antimicrobial Peptide Hydrogels.

Helicobacter pylori can cause various gastric conditions including stomach cancer in an acidic environment. Although early H. pylori infections can be treated by antibiotics, prolonged antibiotic administrations may lead to the development of antimicrobial resistance, compromising the effectiveness of the treatments. Antimicrobial peptides (AMPs) have been reported to possess unique advantages against antimicrobial-resistant bacteria due to their rapid physical membrane disruptions and anti-inflammation/immunoregulation properties. Herein, we have developed an AMP hydrogel, which can be orally administered for the treatment of H. pylori infection. The hydrogel has potent antimicrobial activity against H. pylori, achieving bacterial eradication within minutes of action. Compared with the AMP solution, the hydrogel formulation significantly reduced the cytotoxicity and enhanced proteolytic stability. In vivo experiments suggested that the hydrogel formed at pH 4 had superior therapeutic effects to those at pH 7 and 10 hydrogels, attributed to its rapid release and bactericidal action within the acidic stomach environment. Compared to conventional antibiotic treatments, the AMP hydrogel had the advantages of fast bacterial killing in the gastric juice and obviated proton pump inhibitors during the treatment. Although both the AMP hydrogel and antibiotics suppressed the expression of pro-inflammatory cytokines, the former uniquely promoted inflammation resolution. These results indicate that the AMP hydrogels with effectiveness and biosafety may be potential candidates for the clinical treatment of H. pylori infections.

Peptide Self-assembly: From Ordered to Disordered.

Biomolecular self-assembly is a ubiquitous occurrence in nature that gives rise to sophisticated superstructures that enable the implementation of complex biological functions. It encompasses both ordered structures, such as the DNA double helix, and disordered structures, such as the nucleolus and other nonmembranous organelles. In contrast to these highly organized ordered structures, which exhibit specific patterns or symmetry, disordered structures are characterized by their flexible and randomized molecular organization, which provides versatility, dynamicity, and adaptability to biological systems and contributes to the complexity and functionality of living organisms. However, these disordered structures usually exist in a thermodynamically metastable state. This means that these disordered structures are unstable and difficult to observe due to their short existence time. Achieving disordered structures through precise control of the assembly process and ensuring their stability and integrity pose significant challenges. Currently, ongoing research efforts are focused on the self-assembly of proteins with intrinsically disordered regions (IDRs). However, the structural complexity and instability of proteins present prohibitive difficulties in elucidating the multiscale self-assembly process. Therefore, simple peptides, as a segment of proteins, hold great promise in constructing self-assembly systems for related research. Since our finding on droplet-like disordered structures that occur transiently during the peptide self-assembly (PSA), our research is centered around the dynamic evolution of peptide supramolecular systems, particularly the modulation of a variety of assembled structures ranging from ordered to disordered.In this Account, we narrate our recent research endeavors on supramolecular structures formed by PSA, spanning from ordered structures to disordered structures. We delve into the mechanisms of structural regulation, shedding light on how these peptide-based structures can be controlled more precisely. Moreover, we emphasize the functional applications that arise from these structures. To begin, we conduct a comprehensive overview of various types of ordered structures that emerge from PSA, showcasing their diverse applications. Following, we elaborate on the discovery and development of droplet-like disordered structures that arise during PSA. A mechanistic study on multistep self-assembly processes mediated by liquid-liquid phase separation (LLPS) is critically emphasized. Ordered structures with different morphologies and functions can be obtained by subtly controlling and adjusting the metastable liquid droplets. In particular, we have recently developed solid glasses with long-range disorder, including noncovalent biomolecular glass based on amino acid and peptide derivatives, as well as high-entropy glass based on cyclic peptides. This demonstrates the great potential of using biologically derived molecules to create green and sustainable glassy materials.

Molecular Engineering of Ordered Piezoelectric Sulfonic Acid-Containing Assemblies.

Sulfonic acid-containing bioorganic monomers with wide molecular designability and abundant hydrogen bonding sites hold great potential to design diverse functional biocrystals but have so far not been explored for piezoelectric energy harvesting applications due to the lack of strategies to break the centrosymmetry of their assemblies. Here, a significant molecular packing transformation from centrosymmetric into non-centrosymmetric conformation by the addition of an amide terminus in the sulfonic acid-containing bioorganic molecule is demonstrated, allowing a high electromechanical response. The amide-functionalized molecule self-assembles into a polar supramolecular parallel ß-sheet-like structure with a high longitudinal piezoelectric coefficient d11 = 15.9 pm V-1 that produces the maximal open-circuit voltage of >1 V and the maximal power of 18 nW in nanogenerator devices pioneered. By contrast, molecules containing an amino or a cyclohexyl terminus assemble into highly symmetric 3D hydrogen bonding diamondoid-like networks or 2D double layer structures that show tunable morphologies, thermostability, and mechanical properties but non-piezoelectricity. This work not only presents a facile approach to achieving symmetry transformation of bioorganic assemblies but also demonstrates the terminal group and the property correlation for tailor-made design of high-performance piezoelectric biomaterials.

Biomolecular glass with amino acid and peptide nanoarchitectonics.

Glass is ubiquitous in life and widely used in various fields. However, there is an urgent need to develop biodegradable and biorecyclable glasses that have a minimal environmental footprint toward a sustainable society and a circular materials economy. Here, we report a family of eco-friendly glasses of biological origin fabricated using biologically derived amino acids or peptides through the classic heating-quenching procedure. Amino acids and peptides with chemical modification at their ends are found able to form a supercooled liquid before decomposition and eventually glass upon quenching. These developed glasses exhibit excellent glass-forming ability and optical characteristics and are amenable to three-dimensional-printed additive manufacturing and mold casting. Crucially, the glasses show biocompatibility, biodegradability, and biorecyclability beyond the currently used commercial glasses and plastic materials.

Supramolecular Nanofibrils Formed by Coassembly of Clinically Approved Drugs for Tumor Photothermal Immunotherapy.

Pancreatic cancer, one of the most lethal malignancies, compromises the performance of traditional therapeutic regimens in the clinic because of stromal resistance to systemic drug delivery and poor prognosis caused by tumor metastasis. Therefore, a biocompatible therapeutic paradigm that can effectively inhibit pancreatic tumor growth while simultaneously eliminating tumor metastasis is urgently needed. Herein, supramolecular nanofibrils are fabricated through coassembly of clinically approved immunomodulatory thymopentin and near-infrared indocyanine green for localized photothermal immunotherapy of pancreatic tumors. The resulting long-range ordered fibrous nanodrugs show improved photophysical capabilities for fluorescence imaging and photothermal conversion and significantly promote the proliferation and differentiation of antitumor immune cells. Hence, the integration of rapid photothermal therapy and moderate immunomodulation for inhibiting tumor growth and eliminating tumor metastasis is promising. The utilization of clinically approved molecules to construct nanodrugs administered via localized injection amplifies the complementary photothermal immunotherapeutic effects of the components, creating opportunities for clinical translation as a treatment for pancreatic cancer.

Metal-Free Nanoassemblies of Water-Soluble Photosensitizer and Adenosine Triphosphate for Efficient and Precise Photodynamic Cancer Therapy.

Engineering photosensitizers into stimuli-responsive supramolecular nanodrugs allows enhanced spatiotemporal delivery and controllable release of photosensitizers, which is promising for dedicated and precise tumor photodynamic therapy. Complicated fabrication for nanodrugs with good tumor accumulation capability and the undesirable side-effects caused by the drug components retards the application of PDT in vivo. The fact that extracellular adenosine triphosphate (ATP) is overexpressed in tumor tissue has been overlooked in fabricating nanomedicines for tumor-targeting delivery. Hence, herein we present metal-free helical nanofibers formed in aqueous solution from the coassembly of a cationic porphyrin and ATP as a nanodrug for PDT. The easily accessible and compatible materials and simple preparation enable the nanodrugs with potential in PDT for cancer. Compared to the cationic porphyrin alone, the porphyrin-ATP nanofibers exhibited enhanced tumor-site photosensitizer delivery through whole-body blood circulation. Overexpressed extracellular ATP stabilizes the porphyrin-ATP nanodrug within tumor tissue, giving rise to enhanced uptake of the nanodrug by cancer cells. The enzyme-triggered release of photosensitizers from the nanodrugs upon biodegradation of ATP by intracellular phosphatases results in good tumor therapeutic efficacy. This study demonstrates the potential for employing the tumor microenvironment to aid the accumulation of nanodrugs in tumors, inspiring the fabrication of smart nanomedicines.

Tunable Mechanical and Optoelectronic Properties of Organic Cocrystals by Unexpected Stacking Transformation from H- to J- and X-Aggregation.

Molecular stacking modes, generally classified as H-, J-, and X-aggregation, play a key role in determining the optoelectronic properties of organic crystals. However, the control of stacking transformation of a specific molecule is an unmet challenge, and a priori prediction of the performance in different stacking modes is extraordinarily difficult to achieve. In particular, the existence of hybrid stacking modes and their combined effect on physicochemical properties of molecular crystals are not fully understood. Herein, unexpected stacking transformation from H- to J- and X-aggregation is observed in the crystal structure of a small heterocyclic molecule, 4,4'-bipyridine (4,4'-Bpy), upon coassembly with N-acetyl-l-alanine (AcA), a nonaromatic amino acid derivative. This structural transformation into hybrid stacking mode improves physicochemical properties of the cocrystals, including a large red-shifted emission, enhanced supramolecular chirality, improved thermal stability, and higher mechanical properties. While a single crystal of 4,4'-Bpy shows good optical waveguiding and piezoelectric properties due to the uniform elongated needles and low symmetry of crystal packing, the significantly lower band gap and resistance of the cocrystal indicate improved conductivity. This study not only demonstrates cocrystallization-induced packing transformation between H-, J-, and X-aggregations in the solid state, leading to tunable mechanical and optoelectronic properties, but also will inspire future molecular design of organic functional materials by the coassembly strategy.

Acid-Activatable Transmorphic Peptide-Based Nanomaterials for Photodynamic Therapy.

Inspired by the dynamic morphology control of molecular assemblies in biological systems, we have developed pH-responsive transformable peptide-based nanoparticles for photodynamic therapy (PDT) with prolonged tumor retention times. The self-assembled peptide-porphyrin nanoparticles transformed into nanofibers when exposed to the acidic tumor microenvironment, which was mainly driven by enhanced intermolecular hydrogen bond formation between the protonated molecules. The nanoparticle transformation into fibrils improved their singlet oxygen generation ability and enabled high accumulation and long-term retention at tumor sites. Strong fluorescent signals of these nanomaterials were detected in tumor tissue up to 7 days after administration. Moreover, the peptide assemblies exhibited excellent anti-tumor efficacy via PDT in vivo. This in situ fibrillar transformation strategy could be utilized to design effective stimuli-responsive biomaterials for long-term imaging and therapy.

Porphyrin/Ionic-Liquid Co-assembly Polymorphism Controlled by Liquid-Liquid Phase Separation.

Understanding and controlling multicomponent co-assembly is of primary importance in different fields, such as materials fabrication, pharmaceutical polymorphism, and supramolecular polymerization, but these aspects have been a long-standing challenge. Herein, we discover that liquid-liquid phase separation (LLPS) into ion-cluster-rich and ion-cluster-poor liquid phases is the first step prior to co-assembly nucleation based on a model system of water-soluble porphyrin and ionic liquids. The LLPS-formed droplets serve as the nucleation precursors, which determine the resulting structures and properties of co-assemblies. Co-assembly polymorphism and tunable supramolecular phase transition behaviors can be achieved by regulating the intermolecular interactions at the LLPS stage. These findings elucidate the key role of LLPS in multicomponent co-assembly evolution and enable it to be an effective strategy to control co-assembly polymorphism as well as supramolecular phase transitions.

Coassembly-Induced Transformation of Dipeptide Amyloid-Like Structures into Stimuli-Responsive Supramolecular Materials.

Conformational transition of proteins and peptides into highly stable, ß-sheet-rich structures is observed in many amyloid-associated neurodegenerative disorders, yet the precise mechanism of amyloid formation at the molecular level remains poorly understood due to the complex molecular structures. Short peptides provide simplified models for studying the molecular basis of the assembly mechanism that governs ß-sheet fibrillation processes underlying the formation and inhibition of amyloid-like structures. Herein, we report a supramolecular coassembly strategy for the inhibition and transformation of stable ß-sheet-rich amyloid-derived dipeptide self-assemblies into adaptable secondary structural fibrillar assemblies by mixing with bipyridine derivatives. The interplay between the type and mixing ratio of bipyridine derivatives allowed the variable coassembly process with stimuli-responsive functional properties, studied by various experimental characterizations and computational methods. Furthermore, the resulting coassemblies showed functional redox- and photoresponsive properties, making them promising candidates for controllable drug release and fluorescent imprint. This work presents a coassembly strategy not only to explore the mechanism of amyloid-like structure formation and inhibition at the molecular level but also to manipulate amyloid-like structures into responsive supramolecular coassemblies for material science and biotechnology applications.

Multifunctional Antimicrobial Biometallohydrogels Based on Amino Acid Coordinated Self-Assembly.

There is a real need for new antibiotics against self-evolving bacteria. One option is to use biofriendly broad-spectrum and mechanically tunable antimicrobial hydrogels that can combat multidrug-resistant microbes. Whilst appealing, there are currently limited options. Herein, broad-spectrum antimicrobial biometallohydrogels based on the self-assembly and local mineralization of Ag+ -coordinated Fmoc-amino acids are reported. Such biometallohydrogels have the advantages of localized delivery and sustained release, reduced drug dosage and toxicity yet improved bioavailability, prolonged drug effect, and tunable mechanical strength. Furthermore, they can directly interact with the cell walls and membrane, resulting in the detachment of the plasma membrane and leakage of the cytoplasm. This leads to cell death, triggering a significant antibacterial effect against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria in cells and mice. This study paves the way for developing a multifunctional integration platform based on simple biomolecules coordinated self-assembly toward a broad range of biomedical applications.

Injectable self-assembled bola-dipeptide hydrogels for sustained photodynamic prodrug delivery and enhanced tumor therapy.

Supramolecular peptide materials have attracted increasing attention due to their natural biological origin and versatile applications. However, it is often challenging to control and modulate the self-assembly of peptides (especially short peptides) for constructing hydrogels with tunable mechanical properties and adaptive injectability toward biomedical applications. Here, we report a supramolecular strategy for forming robust and injectable hydrogels based on the self-assembly of a rationally designed bola-dipeptide. The self-assembled hydrogels exhibit versatile functionalities, including flow under shear stress, good recovery properties, and easy encapsulation of hydrophilic prodrugs. The prodrug-loaded hydrogels show sustained release profiles, inhibited nontargeted leakage, and enhanced localized prodrug conversion, leading to highly efficient photodynamic tumor ablation. Hence, the supramolecular strategy is promising for the rational construction of injectable hydrogels toward targeted and sustained prodrug conversion and tumor therapy.

Nucleation and Growth of Amino Acid and Peptide Supramolecular Polymers through Liquid-Liquid Phase Separation.

The transition of peptides and proteins from the solution phase into fibrillar structures is a general phenomenon encountered in functional and aberrant biology and is increasingly exploited in soft materials science. However, the fundamental molecular events underpinning the early stages of their assembly and subsequent growth have remained challenging to elucidate. Here, we show that liquid-liquid phase separation into solute-rich and solute-poor phases is a fundamental step leading to the nucleation of supramolecular nanofibrils from molecular building blocks, including peptides and even amphiphilic amino acids. The solute-rich liquid droplets act as nucleation sites, allowing the formation of thermodynamically favorable nanofibrils following Ostwald's step rule. The transition from solution to liquid droplets is entropy driven while the transition from liquid droplets to nanofibrils is mediated by enthalpic interactions and characterized by structural reorganization. These findings shed light on how the nucleation barrier toward the formation of solid phases can be lowered through a kinetic mechanism which proceeds through a metastable liquid phase.

Cyclic dipeptide nanoribbons formed by dye-mediated hydrophobic self-assembly for cancer chemotherapy.

Cyclic dipeptides (CDPs), the smallest naturally occurring cyclic peptides, have attracted tremendous attention due to their exceptional biological and pharmacological activities such as antitumor, antimicrobial, and immune regulation. However, controlled fabrication of CDPs nanostructures to address the problem of poor aqueous solubility and low bioavailability existing in therapeutic application is still in challenging, due to their remarkable structural rigidity and superior hydrogen-bonding-forming capability. Herein, a simple but robust and universal strategy for the construction of CDP nanoribbons based on the amphiphilic dye-mediated hydrophobic self-assembly is presented. The amphiphilic dyes not only provide the robust hydrophobic interaction for the formation of CDP nanoribbons but also offer enough electrostatic repulsion forces to stabilize the formed assemblies. Moreover, the introduction of functional dyes endows the assembled CDP nanoribbons multiple benign therapeutic features, including adjustable shape and size, improved bioavailability, as well as preferable cellular uptake and biodistribution, thereby enhanced chemotherapy efficacy in vitro and in vivo. The strategy developed based on the dye-mediated self-assembly provides a promising way to rationally design water-insoluble bioactive CDPs for therapeutic applications.

Metal-Ion Modulated Structural Transformation of Amyloid-Like Dipeptide Supramolecular Self-Assembly.

The misfolding of proteins and peptides potentially leads to a conformation transition from an α-helix or random coil to ß-sheet-rich fibril structures, which are associated with various amyloid degenerative disorders. Inhibition of the ß-sheet aggregate formation and control of the structural transition could therefore attenuate the development of amyloid-associated diseases. However, the structural transitions of proteins and peptides are extraordinarily complex processes that are still not fully understood and thus challenging to manipulate. To simplify this complexity, herein, the effect of metal ions on the inhibition of amyloid-like ß-sheet dipeptide self-assembly is investigated. By changing the type and ratio of the metal ion/dipeptide mixture, structural transformation is achieved from a ß-sheet to a superhelix or random coil, as confirmed by experimental results and computational studies. Furthermore, the obtained supramolecular metallogel exhibits excellent in vitro DNA binding and diffusion capability due to the positive charge of the metal/dipeptide complex. This work may facilitate the understanding of the role of metal ions in inhibiting amyloid formation and broaden the future applications of supramolecular metallogels in three-dimensional (3D) DNA biochip, cell culture, and drug delivery.

Self-Assembling Endogenous Biliverdin as a Versatile Near-Infrared Photothermal Nanoagent for Cancer Theranostics.

Photothermal nanomaterials that integrate multimodal imaging and therapeutic functions provide promising opportunities for noninvasive and targeted diagnosis and treatment in precision medicine. However, the clinical translation of existing photothermal nanoagents is severely hindered by their unclear physiological metabolism, which makes them a strong concern for biosafety. Here, the utilization of biliverdin (BV), an endogenic near-infrared (NIR)-absorbing pigment with well-studied metabolic pathways, to develop photothermal nanoagents with the aim of providing efficient and metabolizable candidates for tumor diagnosis and therapy, is demonstrated. It is shown that BV nanoagents with intense NIR absorption, long-term photostability and colloidal stability, and high photothermal conversion efficiency can be readily constructed by the supramolecular multicomponent self-assembly of BV, metal-binding short peptides, and metal ions through the reciprocity and synergy of coordination and multiple noncovalent interactions. In vivo data reveal that the BV nanoagents selectively accumulate in tumors, locally elevate tumor temperature under mild NIR irradiation, and consequently induce efficient photothermal tumor ablation with promising biocompatibility. Furthermore, the BV nanoagents can serve as a multimodal contrast for tumor visualization through both photoacoustic and magnetic resonance imaging. BV has no biosafety concerns, and thereby offers a great potential in precision medicine by integrating multiple theranostic functions.

The Dominant Role of Oxygen in Modulating the Chemical Evolution Pathways of Tyrosine in Peptides: Dityrosine or Melanin.

In diverse biological systems, the oxidation of tyrosine to melanin or dityrosine is crucial for the formation of crosslinked proteins and thus for the realization of their structural, biological, and photoactive functionalities; however, the predominant factor in determining the pathways of this chemical evolution has not been revealed. Herein, we demonstrate for tyrosine-containing amino acid derivatives, peptides, and proteins that the selective oxidation of tyrosine to produce melanin or dityrosine can be readily realized by manipulating the oxygen concentration in the reaction system. This oxygen-dependent pathway selection reflects the selective chemical evolution of tyrosine to dityrosine and melanin in anaerobic and aerobic microorganisms, respectively. The resulting melanin- and dityrosine-containing nanomaterials reproduce key functions of their natural counterparts with respect to their photothermal and photoluminescent characteristics, respectively. This work reveals the plausible role of oxygen in the chemical evolution of tyrosine derivatives and provides a versatile strategy for the rational design of tyrosine-based multifunctional biomaterials.

Amino Acid Coordination Driven Self-Assembly for Enhancing both the Biological Stability and Tumor Accumulation of Curcumin.

Clinical translation of curcumin has been highly obstructed by the rapid degradation and poor tissue absorption of this agent. Herein, we report on the generation of supramolecular curcumin nanoagents through amino acid coordination driven self-assembly to simultaneously increase the biological stability and tumor accumulation of curcumin. The biological stability of curcumin was significantly improved both through coordination and through molecular stacking. The sizes of these nanoagents can be readily manipulated to facilitate tumor accumulation. These favorable therapeutic features, together with high drug-loading capacities and responses to pH and redox stimuli, substantially enhanced the antitumor activity of curcumin without discernible side effects. Hence, supramolecular curcumin nanoagents may hold promise in moving forward the clinical application of curcumin as an effective anticancer drug.

Smart Peptide-Based Supramolecular Photodynamic Metallo-Nanodrugs Designed by Multicomponent Coordination Self-Assembly.

Supramolecular photosensitizer nanodrugs that combine the flexibility of supramolecular self-assembly and the advantage of spatiotemporal, controlled drug delivery are promising for dedicated, precise, noninvasive tumor therapy. However, integrating robust blood circulation and targeted burst release in a single photosensitizer nanodrug platform that can simultaneously improve the therapeutic performance and reduce side effects is challenging. Herein, we demonstrate a multicomponent coordination self-assembly strategy that is versatile and potent for the development of photodynamic nanodrugs. Inspired by the multicomponent self-organization of polypeptides, pigments, and metal ions in metalloproteins, smart metallo-nanodrugs are constructed based on the combination and cooperation of multiple coordination, hydrophobic, and electrostatic noncovalent interactions among short peptides, photosensitizers, and metal ions. The resulting metallo-nanodrugs have uniform sizes, well-defined nanosphere structures, and high loading capacities. Most importantly, multicomponent assembled nanodrugs have robust colloidal stability and ultrasensitive responses to pH and redox stimuli. These properties prolong blood circulation, increase tumor accumulation, and enhance the photodynamic tumor therapeutic efficacy. This study offers a new strategy to harness robust, smart metallo-nanodrugs with integrated flexibility and multifunction to enhance tumor-specific delivery and therapeutic effects, highlighting opportunities to develop next-generation, smart photosensitizing nanomedicines.